Preheating of the air supply to locomotive water tube boiler furnaces



Sept. 18, 1934 H. E. YARROW ET AL PREHEATING OF THE AIR SUPPLY TO LOCOMOTIVE WATER TUBE BOILER FURNACES Filed Feb. '7, 1930 2 Sheets-Sheet l INVE NTORS. Harold E. Yarrow mww W v B I Sep 18, 1934- H. E. YARROW 'ET AL PREHEATING OF THE AIR SUPPLY TO LOCOMOTIVE WATER TUBE BOILER FURNACES Filed Feb. 7, 1930 2 Sheets-Sheet 2 INVENTOR 5 Hqrol d E. Yava qw,

AT TORNE'Y Patented Sept. 18, 1934 UNITED STATES PREHEATING OF THE AIR SUPPLY TO LOCOMOTIVE WATER TUBE BOILER FURNACES Harold Edgar Yarrow, Scotstoun, Scotland, and Herbert Nigel Gresley, Hadley Wood, England Application February 7, 1930, Serial No. 426,641 In Great Britain November 1, 1929 2 Claims.

This invention relates to water tube boilers for locomotives and particularly to the pre-heating of a portion or the whole of the air supply to the furnaces of such boilers by taking in air at the front end of a longitudinal double casing which substantially encloses the boiler and smoke box, and delivering the air, thus heated during its passage by the absorption of heat radiated from the furnace gas fines and fire box, to the ash pan and thereby utilizing heat which would otherwise be lost.

According to the present invention, the outer casing is continued beyond the front of the smoke box on both sides of the locomotive and so forms a plenum chamber when the locomotive is travelling, and air inlets are provided in the side walls of this chamber so that rain or snow or dust will not be driven into the air passage. Additional air inlets may also be provided in the front end of the extended air casing, and both sets of inlets may be fitted with adjustable louvres or any equivalent device for regulating the air supply.

One embodiment of the invention is illustrated in the accompanying drawings, wherein Fig. 1 g is a side elevation of a locomotive boiler showing the essential parts of the apparatus involved in the invention; Fig. 2 is a plan View of same; Fig. 3 is a transverse section, the left half taken on line A-A and the right half on line B-B in Fig. 1 looking in the direction of the arrows; Fig. 4 is an elevation of the smoke box end of the boiler; Fig. 5 is an elevation of the fire box end of the boiler, and Fig. 6 is a perspective view of the smokebox end of the boiler showing the plenum chamber.

In these drawings the locomotive boiler is designated generally by the letter A and, as shown, this boiler comprises an upper steam and water drum B and lower water drums C, C connected with the drum B by water tubes D, B respectively.

The air jacket or pre-heater is formed between an outer longitudinal casing 1 and an inner longitudinal casing 1 which is usually the boiler casing itself. The outer casing is carried forward beyond the smoke box so as to form a kind of plenum chamber 7 in front of the smoke box 13 when the locomotive is travelling in a forward direction, from which chamber air under pressure passes into the air jacket or pre-heater. Forwardly projecting portions or wings of the air ducts 2 and 2' form the side walls 8 and 9 of the plenum chamber 7, and a transverse plate 11 extending between the side walls 8 and 9 of the plenum chamber with its upper edge abutting the under side of the boiler casing l forms the rear wall of the plenum chamber, while the front plate or sill 12 of the engine frame forms the floor of said chamber. The plenum chamber may be open at the top except in so far as it may be overhung by the smokebox.

Air inlets 8 9 are provided in the side walls or wings 8, 9 of this plenum chamber, these air inlets being preferably fitted with adjustable louvres or other means for regulating the admission of air. With this arrangement of the front end of the pre-heater, as the locomotive moves forward air trapped in the plenum chamber '7 will be forced through the air inlets 8 and 9 and the preheating of the whole preheated air supply for the furnace, or a portion thereof, is ensured. In its passage along these ducts the air absorbs heat from the flues 3 and also from the sides of the fire box 4, thereby not only utilizing heat which would otherwise be lost, but also keeping the casings cool and thus reducing radiation losses.

From the rear end of the fire box the air is led downwards around the fire door 4 by the ducts 5 and 5 whence it passes to the ash pan 6, entering at the rear end 6 thereof. In the drawings the ducts 5 are shown as being between the frames, but they may alternatively be arranged outside the frames of the locomotive.

If desired, additional air inlets 10 may be provided at the front end of the casing 1 in the portions 10 thereof which extend forwardly beyond the front end of the smoke box and then toward one another, and such inlets would also preferably be provided with louvres not merely for regulation of the air supply, but also for the exclusion of rain or the like.

Having thus described the nature of the said invention and the best means we know of carrying the same into practical effect, we claim:-

1. In a locomotive comprising a firebox, a boiler, a smoke box and a front sill, means for supplying air to the firebox and in which it is preheated, said means comprising inner and outer casings extending longitudinally of the boiler from the front end of the smoke box and forming a jacket which communicates at its rear end with the firebox, the forward end of said inner casing terminating at approximately the front end of said smoke box and said outer casing having portions extending forwardly beyond 7 the front end of the smoke box and then toward one another, a pair of wings extending forwardly from the front end of the smoke box and respectively closing the spaces between the latter and the forward portions of the outer casing which 2. A locomotive according to claim 1 wherein the portions of the outer casing which extend toward one another have additional air inlets.

HAROID EDGAR YARROW. HERBERT NIGEL GRESLEY. 

